This invention claims priority of the German patent application 101 02 542.4 which is incorporated by reference herein.
The invention refers to an arrangement for the visual inspection of substrates, equipped with a microscope for viewing a portion of the substrate located at an inspection point.
Arrangements of this kind are used in particular in semiconductor production for the inspection of wafers, in order to examine them for manufacturing defects. An arrangement of this kind is, for example, marketed by the LEICA company under the designation INS 3000. This arrangement, which is depicted schematically in FIG. 7 and FIG. 8, comprises a transport device 4 with which wafers having diameters from 100 to 200 mm are delivered to inspection point I. At inspection point I, portions of the wafer to be inspected can be viewed with the aid of a microscope.
A monitor 15 is additionally set up next to the microscope. On this monitor 15, the viewer is offered a function menu that displays various setting options for the inspection arrangement, for example the type of illumination for a wafer to be inspected, or an opportunity to select an examination region on the wafer. In addition, an image of the wafer presently being examined, or of a portion of that wafer, can be displayed on monitor 15 so that defects on the wafer can also be detected on the basis of the monitor image.
During inspection, an operator sits or stands in front of the microscope and views through its eyepiece 10 the wafer or the portion of interest of that wafer. In this viewing position, which is labeled P1 in FIG. 7 and FIG. 8, the operator can control the operation of the inspection arrangementxe2x80x94for example the advance movement upon transport of a wafer into the inspection position, selection of a region to be examined on the wafer, and the likexe2x80x94by way of the control console present in front of him or her, without changing his or her position. Because of its orientation parallel to eyepieces 10 of the microscope, however, the monitor set up next to the microscope is poorly visible, since its most favorable viewing position P2 is located right alongside operating position P1.
In addition, in inspection arrangements of this kind such as those also known, for example, under the designation xe2x80x9cOptistation 7xe2x80x9d of the Nikon company, the monitor is arranged too close to the operator. Because of the working distance that must be maintained, in such cases it is possible to use only a relatively small monitor on which details are sometimes difficult to recognize.
Proceeding from this existing art, it is the object of the invention to develop further an arrangement of the kind cited initially with ergonomics in mind and with the criterion of a compact design.
For that purpose, according to the present invention at least one viewing field for viewing an image or an image area of the substrate, and/or at least one further viewing field for direct viewing of the substrate or a portion of the substrate, is provided next to the microscope viewing port. The microscope viewing port and the viewing fields are arranged with respect to an operating position in such a way that from the operating position, the viewer looks in a first viewing direction perpendicularly onto the microscope viewing port, and in at least one further viewing direction approximately perpendicularly in each case onto one of the viewing fields. In addition, the first viewing direction encloses an acute angle in each case with the further viewing direction or directions.
This allows the operator to work in relaxed and fatigue-free fashion, since it is now possible, from the operating position, to look with a slight inclination or rotation of the head substantially perpendicularly onto the viewing fields present next to the microscope viewing port. The result of this is better identifiability in the region of the viewing fields, as a result of which the error rate during inspection of the wafers can be reduced.
Because of the oblique position of the viewing field with respect to the operating position, the distance between the operating position and the viewing field is moreover increased, so that the latter can be made larger than previously. It is thus possible, for example, to display more operating options or to show a larger image of the portion of the substrate presently being examined.
In a particularly advantageous embodiment of the invention, the arrangement furthermore comprises a housing that surrounds the inspection point of the microscope. The microscope itself is for the most part received in the housing. The viewing field or fields furthermore is or are integrated into one of the outer walls of the housing. This encapsulation not only is attractive in terms of external appearance, but also, principally, allows inspection of the substrates under enhanced cleanliness conditions. For example, an enhanced level of cleanliness can be confined to the interior of the housing. In addition, the encapsulation prevents the risk of operator error or improper actions when positioning the substrates on the inspection point of the microscope. The encapsulation furthermore contributes to workplace safety for the operator.
In a further advantageous embodiment of the invention, a conveying device is additionally provided for transporting the substrates to and away from the inspection point. The control instructions for the conveying device, which is arranged inside the housing, can be entered via the control console.
Furthermore, at least one magazine for receiving the substrates can be integrated into the arrangement, a transfer device for transferring substrates between the magazine and the conveying device additionally being provided. The result is to create a completely closed module for substrate inspection that can be set up, for example, in the vicinity of a wafer production line. Interchangeable magazines are preferably used in this context, thus making possible faster exchange of the substrates to be examined. The magazine or magazines can be configured as separate modules that can be connected to the housing of the inspection arrangement.
For an ergonomically favorable arrangement of the viewing field or fields, it is moreover advantageous if the first viewing direction encloses an angle of less than 50xc2x0 with the further viewing directions, the operating position being located approximately at the vertex. In practice, angles in the range from 30xc2x0 to 40xc2x0 have proven particularly ergonomically favorable.
In a particularly advantageous embodiment, one viewing field is arranged in the horizontal direction on each of the two sides of the microscope viewing port. This thus makes possible, as it were, a panoramic view from the operating position, in which the angle of view is based on operator""s natural field of view.
Preferably the two viewing fields are positioned in ergonomically favorable fashion at the same viewing height. In addition, the respective viewing directions toward the viewing fields can enclose identical angles with the first viewing direction, i.e. toward the microscope viewing port. This results in a symmetrical arrangement with respect to the microscope arranged in the middle.
It is not necessary, however, to provide two viewing fields.
A monitor on which an image or image area of the substrate can be visualized is preferably arranged in one viewing field. It is thereby possible to analyze the substrate or a portion thereof with particularly high accuracy. In a particularly simple variant embodiment, this monitor alone serves to provide information about the substrate to be inspected.
It is possible in principle to display on the monitor images of the substrate that are obtained outside the inspection point of the microscope. In a particularly advantageous embodiment of the invention, however, images of the substrate or of parts thereof are generated with the aid of the microscope on the monitor. For that purpose, the microscope is coupled to an optoelectronic camera and the latter is connected via an electronic image processing device to the monitor.
In a further embodiment of the invention, one viewing field is configured as a transparent panel through which a substrate position can be looked at directly. In this fashion, for example, transportation of the substrates into the inspection position can be easily observed and monitored.
A wobbler having a plate for holding a substrate can be arranged in the visible region of the viewing field behind the transparent panel. This plate can rotate about a rotation axis and can tilt with respect to the rotation axis. Upon rotation of the plate, a substrate held thereon performs a wobbling motion so that the substrate can be viewed from the operating position from different angles of view. This makes it possible, in particular, to verify scratches or contaminants such as dust particles on the substrate as defects.
If the inspection region is imaged through the microscope and displayed on a monitor, it is not absolutely necessary to use the microscope viewing port for inspection. The possibility of observation through the microscope is desirable in most cases, however, and the microscope is preferably configured as a stereomicroscope having two eyepieces.
For ergonomic reasons, the eyepieces and the viewing fields are preferably arranged at one height. The operator can thus rapidly change viewing directions with a small head movement, and can look either through the eyepieces or, for a quick visual check, at the viewing field or fields.
In order to prevent excessive leaning over the control console and an unfavorable head posture on the part of the operator during inspection, the eyepieces preferably extend over the control console. It is advantageous in terms of a compact design to arrange the control console as close as possible to the housing. In order still to make possible a sufficient viewing distance to the viewing fields in such a case, the latter are arranged in a recess of the outer wall of the housing. To make possible a rapid change in viewing direction, a distance of preferably approximately 30 cm is provided in each case between the eyepieces and a viewing field.